release.txt
MODFLOW-NWT Release Notes
This file describes changes introduced into MODFLOW-NWT with each official
release; these changes may substantially affect users.
NOTE: Any use of trade, product or firm names is for descriptive purposes
only and does not imply endorsement by the U.S. Government.
o Version 1.0.8 09/24/2013:
A significant change to MODFLOW-NWT for this release was the addition of the Seawater
Intrusion (SWI2) Package for MODFLOW (Bakker and others, 2013). Refer to the SWI2
documentation report available at http://pubs.usgs.gov/tm/6a46/ for details regarding
the functionality and input required for SWI2. Modifications to MODFLOW-NWT that were
made to support SWI2 include the addition of one new source code file (gwf2swi27_NWT.f)
and the addition of call statements added to the MODFLOW-NWT main source code file
(MF_NWT.f).
Lake (LAK) Package
A bug was fixed to correctly print lake seepage to unformatted budget files. This
bug affects models with lake cells that are surrounded by inactive groundwater cells
in the same lake.
Streamflow Routing (SFR2) Package
A bug was fixed to avoid a memory-allocation error that occured when using
the tabfile option for models with more tabfiles than stream segments. Also,
an unitialized variable was initialized.
Subsidence (SUB) Package
Support was added for the Subsidence Package using the NWT solver and Upstream-Weighting
Flow Package. Changes to the code consist of setting storage changes related to subsidence
to zero when head falls below the cell bottom.
Unsaturated-Zone Flow (UZF1) Package
A bug was fixed to allow the vertical hydraulic conductivity to be read when
IUZFOPT=-1; that is, when unsaturated-zone storage is ignored and infiltrated water
is added directly to the water table.
The maximum root depth was reduced from extending through 99% of the cell thickness
to 90% of the cell thickness. This improves convergence for models where the root
depth extends to the bottom of the cell.
Initialization was added for a few variables and checks were added for divide by zero.
Surface-Water Routing (SWR1) Process
Additional functionality was added to the SWR1 Process incorporated in
MODFLOW-NWT. The modifications to the SWR1 Process (version 1.03) are documented in the
document titled 'SWRProcess_release.txt' included with this distribution. Complete SWR
input instructions for version 1.03 are provided in:
'..\MODFLOW-NWT_1.0.8\doc\SWRProcessInputInstructions_v1.03.pdf' included with this
distribution.
SWR test problems 1-4 have been removed from the distribution but are still available
at http://water.usgs.gov/ogw/swr/. SWR test problems 1-4 are surface-water only problems
and do not use the functionality of MODFLOW-NWT. SWR test problem 5 is a coupled
surface-water/groundwater problem that does use the functionality of MODFLOW-NWT.
MODFLOW-NWT Main file
At the onset of each time step, groundwater heads were set to their values one iteration
prior to convergence after each times step. This change has no effect on the solution but
was made for consistancy with the standard Newton solution approach.
Link-MT3DMS (LMT) Package
A bug was fixed to print the fluxes coming out of the bottom of dry cells. This change
will have a significant effect on transport solutions for groundwater flow problems
that contain dry cells with fluxes moving through them.
Source files that were modified for this release include:
gwf2lak7_NWT.f, gwf2sfr7_NWT.f, gwf2sub7_NWT.f, gwf2uzf1_NWT.f, MF_NWT.f, lmt7_NWT.f,
gwf2swi27_NWT.f, gwf2swr7_NWT.f, gsol7.f
o Version 1.0.7 01/15/2013:
Lake (LAK) Package
In versions of MODFLOW-NWT prior to 1.0.6, when the Lake Package was used simultaneously
with the HUF Package, the effective (combined) aquifer-lakebed conductances were
not calculated correctly. In this update, the Lake Package has been modified to
compute effective lake-aquifer conductance solely on the basis of the user-specified
value of lakebed leakance; aquifer hydraulic conductivities are not used in this
calculation. An appropriate informational message is now printed after the lakebed
conductances are written to the main output file. There have also been several minor
changes to format statements to improve the information content of the output file.
Multi-Node Well (MNW2) Package
An argument mismatch was corrected between the call to the subroutine GWF2MNW27RP
from MF_NWT.f to gwf2mnw27_NWT.f.
A bug was fixed that affected simulations in which a composite well screen was
generated when specifying multiple open intervals by elevation. In this case,
some nodes were inadvertently excluded from the second interval. With the fix,
all nodes of the multi-node well will be represented. Some output format
adjustments were also made.
If a single-node multi-node well with a nonzero specified discharge was located
in an inactive cell (IBOUND=0), it could generate a divide-by-zero error and
halt execution of the program. The code was fixed to preclude such a
floating-point error from occurring. A new warning message is now also written to
the output file if this condition is detected.
If the well yield (and pumping rate) was reduced because of the seepage face
calculations, an incorrect message (indicating erroneously that the cause was the
head constraint) was written to the output file. The code was fixed so that
possible causes of reduced pumping rates are accurately printed.
The code was modified to eliminate separate processing for single-node MNW2 wells,
which eliminated some inconsistencies in handling single-node wells. If the computed
value for the head in single-node wells drops below the bottom of the cell, it invokes
the seepage face calculation, which will reduce or eliminate the desired Q from the
well. In cases where the Qdes is thereby reduced, the actual head in the well is
indeterminate, but will be reported in separate MNWI output files as the limiting
value of the bottom elevation of the cell together with an information note that the
actual value may be lower than that reported value. If Qdes is reduced to zero, the
well is deactivated and that information is reported in the MNWI optional MNW2
observation well file.
At the end of the first paragraph on p. 32 of the documentation report, it states that
the alternate calculations for CWC for nonvertical wells will be performed automatically
when LOSSTYPE = THIEM, SKIN, or GENERAL. Unfortunately, the code did not check this
condition, and erroneously performed these calculations when LOSSTYPE = SPECIFYCWC.
The corrected code now uses the specified values of CWC for nonvertical wells when it
is supposed to.
The code automatically estimates the maximum number of nodes (NODTOT) as required for
allocation of arrays. However, if a large number of horizontal wells are being simulated,
or possibly for other reasons, this default estimate proves to be inadequate, a new
input option has been added to allow the user to directly specify a value for NODTOT. If
this is a desired option, then it can be implemented by specifying a negative value for
"MNWMAX"--the first value listed in Record 1 (Line 1) of the MNW2 input data file. If
this is done, then the code will assume that the very next value on that line will be
the desired value of "NODTOT". The model will then reset "MNWMAX" to its absolute value.
The value of "IWL2CB" will become the third value on that line, etc.
The code included several coding errors in the calculation of cell-to-well conductances
for nonvertical wells. There was also an error in the calculation of the length of closed
casing between sequential, but non-adjacent, active nodes of a nonvertical MNW2 well (a
value only used for informational purposes in the output file). All of these errors have
now been fixed.
A bug was fixed that affected simulations when both MNW2 and the HUF Packages
were used in the same simulation in conjunction with the partial penetration
correction. The variable KY is now declared as a Double Precision variable
instead of being implicitly assumed (incorrectly) to be an Integer variable.
A number of minor changes were made in Format statements to produce a cleaner
output file.
In Subroutines GWF2MNW27BCF and GWF2MNW27HUF, corrections were made to assure
the correct check is made for steady-state or transient conditions and to prevent
a divide by zero error if a cell is dry.
A bug was fixed for the calculation of angles theta and omega for slanted wells
with an orientation into the southwest directional quadrant.
A bug was fixed that caused erroneous values to be written to the compact budget
file (specifically, for inactive MNW wells), although the numerical solution itself
was accurate, as were the budget numbers written to the main listing file.
Hydrogeologic-Unit Flow (HUF) Package
Small changes were made to make RHS and HCOF double precision when passed as
subroutine arguments.
Preconditioned Conjugate Gradient (PCG) Package
Small changes were made to make RHS and HCOF double precision when passed as
subroutine arguments.
NWT Main File (MF_NWT.f)
The version number and date were made consistent with MODFLOW-2005 1.9.01, 05/01/2012
Streamflow Routing (SFR2) Package
An uninitialized variable was initialized.
Gage Package
Commas were added to some write statements.
Modified source files: gwf2mnw27_NWT.f, MF_NWT.f, gwf2lak7_NWT.f, gwf2mnw2i7.f,
nogmg.f, gwf2huf7.f, pcg7_NWT.f, gwf2sfr7_NWT.f, gwf2gag7.f
o Version 1.0.6 12/05/2012:
The most significant change to MODFLOW-NWT for this release was the addition of the Surface-
Water Routing Process (Hughes and others, 2012). Refer to the SWR1 documentation report
located in MODFLOW-NWT_1.0.6\doc for details regarding the functionality
and input required for SWR1. Modifications to MODFLOW-NWT that were made to support SWR1
include the addition of two new source code files (gsol7.f and gwf2swr7_NWT.f) and the
addition of call statements added to the MODFLOW-NWT main source code file (MF_NWT.f). Additionally,
there are 5 test problems that use SWR1 included with this release for testing the linkage
between MODFLOW-NWT and SWR1 located in MODFLOW-NWT_1.0.6\data\SWR_data_files. Refer
to the readme files for more details on these test problems and other aspects of SWR1.
Newton Solver
Changes were made to default input values when the key word options are used. These
changes reflect information gained from testing using numerous groundwater models
The defaults values for "SIMPLE," "MODERATE," and "COMPLEX" are now as follows:
"SIMPLE"
IACL = 1, NORDER = 0, LEVEL = 3, NORTH = 5, IREDSYS = 1, All other values remain the same.
"MODERATE"
DBDTHETA = 0.9, NORDER = 0, LEVEL = 5, NORTH = 5, IREDSYS = 1, RRCTOLS = 0.0, IDROPTOL = 1,
EPSRN = 1.0e-4, HCLOSEXMD = 1.0e-4, MXITERXMD = 50, All other values remain the same.
"COMPLEX"
DBDTHETA = 0.85, BACKFLAG=1, MAXBACKITER=50, BACKTOL=1.1, BACKREDUCE=0.7,
LEVEL = 5, IREDSYS = 1,EPSRN = 1.0e-5, HCLOSEXMD = 1.0e-5, MXITERXMD = 100,
All other values remain the same.
Lake (LAK) Package
Moved the read statements for specified lake bathymetry to proceed the stress period information.
This change does not affect results or input instructions. Refer to the updated input
instructions for using external lake bathymetry input files titled "Lake3_Input_Modified.pdf"
located in \MODFLOW-NWT_1.0.6\doc for details. A new test problem was added to the MODFLOW-NWT
release 1.0.6 that demonstrates the use of external bathymetry input files. This problem can
be run by executing the batch file 'l1b2k_bath.bat' located in MODFLOW-NWT_1.0.6\data. Input
for this test problem is located in MODFLOW-NWT_1.0.6\data\Lake_bath_example and output is included
in MODFLOW-NWT_1.0.6\output_test. This test problem is identical to the MODFLOW-2005 test problem
l1b2k documented in Merritt and Konikow (2000) as test problem 1, except for the use of external
bathymetry input files. Thus, the results are unchanged relative to the original results produced
by MODFLOW-2005. Also, a bug was found that affects simulations that use the Hydrologic-Unit Flow
(HUF) Package (Anderman and Hill, 2000). Due to the difficulty in determining the effective
vertical hydraulic conductivity in the HUF Package, the option to use the HUF Package with
the Lake package has been removed from MODFLOW-NWT. Thus, an error will be printed and the
program will stop if the HUF and LAK Packages are used together in a simulation.
WELL (WEL) Package
A bug was fixed to allow the reduced pumping information to be written correctly to the LIST file
or separate text file.
xMD Matrix Solver
Some initialization issues associated with Bi-cgstab and Orthomin were resolved, and some
minor changes were made.
Basic (BAS) package
The variables RHS and HCOF were made double precision.
Upstream Weighting (UPW) Package
Some variables were made double precision and the precision used in calculations
was made consistent. Added an option to turn off the checking that a value is
defined for all cells when parameters are used to define layer data. This option
is implemented by specifying the keyword "NOPARCHECK" as one of the options in
input Item 1 of the UPW input file.
Streamflow Routing (SFR2) Package
Some variables were made double precision and the precision used in calculations
was made consistent. Some minor calculations were modified for solution efficiency.
Allocation of some variables were changed to reduce the amount of random axcess memory (RAM)
required for simulations. These changes did not affect simulation results. Initialization
of some local variables was added.
Unsaturated-Zone Flow (UZF1) Package
Initialization of some local variables was added.
Multi-Node Well (MNW2) Package
Checks were added for calculations that divide real numbers. Changes were made to be
consistent with version released with MODFLOW-2005 v1.9.
General-Head Bounday (GHB) Package
Changes were made to be consistent with version release with MODFLOW-2005 v1.9.
Strongly Implicit Procedure (PCG) Package
The variables RHS and HCOF were made double precision.
Preconditioned Conjugate-Gradient (PCG) Package
The variables RHS and HCOF were made double precision.
Direct Solver (DE) Package
The variables RHS and HCOF were made double precision.
The Stream Observation Package (obs2str7.f) was added.
o Version 1.0.5 05/14/2012:
Newton Solver
Changes were made to fix a bug that caused Hdry to be printed for confined cells that
have heads below the cell bottom altitude. Hdry only will be printed for unconfined
layers.
Changes were made to default input values when the key word options are used. These
changes reflect information gained from testing using numerous groundwater models
The defaults values for "SIMPLE," "MODERATE," and "COMPLEX" are now as follows:
"SIMPLE"
IACL = 1, NORDER = 0, LEVEL = 3, NORTH = 5, IREDSYS = 1, RRCTOLS = 0.0, IDROPTOL = 1
EPSRNS = 1.0e-3, HCLOSEXMDDUM = 1.0e-4, MXITERXMD = 50, All other values remain the same.
"MODERATE"
IACL = 2, NORDER = 1, LEVEL = 5, NORTH = 5, IREDSYS = 1, RRCTOLS = 0.0, IDROPTOL = 1
EPSRNS = 1.0e-3, HCLOSEXMDDUM = 1.0e-4, MXITERXMD = 50, All other values remain the same.
"COMPLEX"
IACL = 2, NORDER = 1, LEVEL = 5, NORTH = 7, IREDSYS = 1, RRCTOLS = 0.0, IDROPTOL = 1
EPSRNS = 1.0e-5, HCLOSEXMDDUM = 1.0e-5, MXITERXMD = 50, All other values remain the same.
xMD Matrix Solver
Some initialization issues associated with Bi-cgstab and Orthomin were resolved, and some
minor changes were made.
Well Package
Changes were made to report wells with reduced pumping due to dewatered conditions
to a separate output file or to the main listing file. If the wells with reduced pumping
rates are written to a separate output file then a file of type "DATA" must be included
in the Name file with a unit number that matches the unit number specified in the
Well file (following the variable PHIRAMP in Item 2b). For example, a value of
PHIRAMP (see MODFLOW-NWT documentation report) of 0.3 and a unit number of 50 can be
specified in the second line of the Well file using the key word "SPECIFY" as:
SPECIFY 0.3 50
The following line must be added to the Name file:
DATA 50 Reduced_wells.out
Thus, wells with reduced pumping will be written for each time step to the output file
"Reduced_wells.out" with unit number 50. For example, wells with reduced pumping will
be reported to file "reduced_wells.out" as:
WELLS WITH REDUCED PUMPING FOR STRESS PERIOD 6 TIME STEP 2
LAY ROW COL APPL.Q ACT.Q GW-HEAD CELL-BOT
4 91 69 -0.104400E+04 -0.104399E+04 0.208142E+04 0.205380E+04
4 91 69 -0.208800E+04 -0.208798E+04 0.208142E+04 0.205380E+04
4 91 69 -0.208800E+04 -0.208798E+04 0.208142E+04 0.205380E+04
WELLS WITH REDUCED PUMPING FOR STRESS PERIOD 6 TIME STEP 3
LAY ROW COL APPL.Q ACT.Q GW-HEAD CELL-BOT
4 91 69 -0.104400E+04 -0.967118E+03 0.207686E+04 0.205380E+04
4 91 69 -0.208800E+04 -0.193424E+04 0.207686E+04 0.205380E+04
4 91 69 -0.208800E+04 -0.193424E+04 0.207686E+04 0.205380E+04
Streamflow-Routing Package
A small bug was fixed that stopped the stream width from being set equal to the
wetted perimeter for ICALC=2. This change only affects the printout of stream
width, and calculations dependent on stream width were made using the correct
value in previous versions of SFR2.
Changes were made to printout all stream reaches with streambed altitudes below
the cell bottom before the model stops due to this error. Previous versions
of the code printed out the first reach encountered with an altitude error
and stopped. This version prints information for all reaches with altitude
errors to the List file before stopping the simulation. An example of this
error printout extracted from the List file is shown below.
REACHES WITH ALTITUDE ERRORS:
LAY ROW COL SEG REACH STR.ELEV. CELL-BOT.
1 4 57 1 57 -1.7500000 0.0000000
1 4 58 1 58 -4.2500000 0.0000000
1 4 59 1 59 -6.7500000 0.0000000
1 4 60 1 60 -9.2500000 0.0000000
1 4 61 1 61 -11.7500000 0.0000000
1 4 62 1 62 -14.2500000 0.0000000
1 4 63 1 63 -16.7500000 0.0000000
1 4 64 1 64 -19.2500000 0.0000000
1 4 65 1 65 -21.7500000 0.0000000
MODEL STOPPING DUE TO REACH ALTITUDE ERROR
Multi-Node Well Package version 2 (MNW2)
Changes were made to the MNW2 Package by the authors of the package
(Konikow and others, 2009) for version 1.9 of MODFLOW-2005. These changes also
were made to this release of MODFLOW-NWT. These changes are:
A bug was fixed that affected simulations when both MNW2 and the HUF Package
were used in the same simulation in conjunction with the partial penetration
correction. The variable KY is now declared as a Double Precision variable
instead of being implicitly assumed (incorrectly) to be an Integer variable.
A number of minor changes were made in Format statements to produce a cleaner
output file.
In Subroutines GWF2MNW27BCF and GWF2MNW27HUF, corrections were made to assure
the correct check is made for steady-state or transient conditions and to prevent
a divide by zero error if a cell is dry.
A bug was fixed for the calculation of angles theta and omega for slanted wells
with an orientation into the southwest directional quadrant.
A bug was fixed that caused erroneous values to be written to the compact budget
file (specifically, for inactive MNW wells), although the numerical solution itself
was accurate, as were the budget numbers written to the main listing file.
Additional changes were made to the MNW2 Package for MODFLOW-NWT. These changes do not
affect simulations using the MNW2 Package with solvers other than the NWT solver within
MODFLOW-NWT. These changes were required to solve instabilities created by seepage face
conditions within a MNW2 well and when a cell containing a MNW2 well becomes dry. The first
change resets the head in a well to the bottom of the cell when it falls below the bottom
of the cell for each node. For certain circumstances this was not occurring. The second
change applies smoothing of the cell-to-well conductance as a cell dries. These changes
may cause small changes to simulation results if these conditions arise (that is, cell
drying or seepage face conditions).
Drain (DRN) Package
A check was added for drain altitudes set below the cell bottom. If this occurs, then
an error is printed to the List file and the model is stopped.
General Head Boundary (GHB) Package
A check was added for head boundaries set to altitudes below the cell bottom. If this occurs, then
an error is printed to the List file and the model is stopped.
River (RIV) Package
A check was added for river heads set to altitudes below the cell bottom. If this occurs, then
an error is printed to the List file and the model is stopped.
Link-MT3DMS (LMT) Package
Changes were made to the Link-MT3DMS file to accommodate the MNW2 fluxes. There was
a bug in the previous version of this file caused by a conflict between MNW1 and MNW2
and the header for the MT3DMS FTL file did not include MNW2. This bug was causing
MT3DMS to read the FTL file incorrectly.
Source files that were modified include: lmt7_NWT.f, lmt7_NWT.inc, gwf2mnw27_NWT.f, gwf2sfr7_NWT.f
gwfsfrmodule_NWT.f, NWT1_xmd.f, and NWT1_xmdlib.f, MF_NWT.f, gwf2drn7_NWT.f, gwf2ghb7_NWT.f,
gwf2riv7_NWT.f
o Version 1.0.4 01/25/2012:
Multi-Node Well (MNW1) Package and the lmt7_NWT.f and lmt7_NWT.inc source files
The name of the data module for in MNW1 was changed from GWFMNWMODULE to GWFMNW1MODULE to discriminate
it from the module in the MNW2 package. This change was required because data used in the lmt7_NWT.f
and lmt7_NWT.inc were being confused with data in the MNW2 Package module. Both the lmt7_NWT.f and
lmt7_NWT.inc files were changed to reflect the new module name.
Streamflow-Routing Package
Modifications were made to allow for negative NSTRM values to be specified in the SFR2 input file.
In versions of SFR2 prior to the version released with MODFLOW-NWT 1.0.3, a negative value of NSTRM
could be specified to simulate unsaturated flow beneath streams and for specifying streambed
information by reach. However, SFR2 released with MODFLOW-NWT 1.0.3 was changed such that negative
values specified for NSTRM would cause an error and the program would stop. SFR2 release with
MODFLOW-NWT 1.0.4 supports both the key word option and a negative value for NSTRM.
See the modified input instructions for SFR2 titled "Updated_SFR2_input_instructions_NWT.pdf"
in the "doc" directory of this release.
The SFR2 variable NUMSEG was added to the Module GWFSFRMODULE.
Source files that were modified include: lmt7_NWT.f, lmt7_NWT.inc, gwf2mnw17_NWT.f, gwf2sfr7_NWT.f
and gwfsfrmodule_NWT.f
o Version 1.0.3 12/29/2011:
NWT Solver
The previous version of the NWT solver would take zero outer iterations if the convergence tolerances
were met during the first calculation of the residuals. However, this condition could result in a poor
solution for some nonlinear problems. At least one iteration is now required for all time steps.
This change could affect convergence for some problems.
There was a bug that was causing the red-black ordering scheme to fail (NWT solver input variable
IREDSYS=1).Red-black ordering can help speed convergence for difficult problems. This change could
affect convergence for some problems.
The header written by the NWT solver to the main Listing file was changed slightly. The header previously
titled "RMS," or if residual control is active "RMS1" and "RMS2," was changed to "L2-NORM," and "L2-NEW"
and "L2-OLD," respectively. This change reflects the true definition of the residual terms because they
are calculated as the L2-NORM and not the root-mean-squared error (RMS error). This change does not
affect simulation results.
A few small changes were made to initialize variables and remove unused variables. These changes likely
would not affect simulation results.
Unsaturated-Zone Flow Package
A bug was found that was introduced to the UZF1 package after 1.0.1 MODFLOW-NWT release. This
bug was causing UZF1 to incorrectly calculate unsaturated-zone ET, which results in much less ET
than solution prior to the 1.0.2 release. This change does effect solution results as
compared to the 1.0.2 version but not compared to 1.0.1 version.
Three new options were added to this package to allow specification of the residual water content
(THTR), to provide the option of specifying initial water content (THTI) for simulations that
begin with a steady-state recharge period, and to turn off calculation of surface leakage.
These changes were made for the following reasons.
THTR originally was calculated internally by the UZF Package on the basis of the difference between the
saturated water content (THTS) and the specific yield (SY) of the aquifer receiving recharge (Niswonger
and others, 2006). However, the ability to specify THTR can be useful for some applications in which the
maximum storage in the unsaturated zone (THTS-THTR)is different than the instantaneous drainage from the
aquifer (SY). For these cases, specifying THTR based on external calculations provides greater
flexibility for parameterizing the unsaturated zone. The option to specify THTR is activated using the
key word SPECIFYTHTR. This key word is input on line 1a of the revised UZF1 input file (see revised
input instructions below). Values for THTR are input following the variable THTS (see below).
Originally, THTI was not specified for simulations that included both a steady-state and one or more
transient stress periods. For this case, THTI was calculated internally by the code on the basis of the
steady-state infiltration rate and the unsaturated-zone hydraulic properties (FINF, FKS, EPS, THTS, and
THTR). However, in well-drained soils, the steady-state recharge rate corresponds to an initial water
content that is too large for coarse sediments. Consequently, drainage from the unsaturated zone during
the first transient stress period could result in an unrealistically large recharge rate. Additionally,
the head dependency on recharge that does not occur during steady-state stress periods but that can
occur during transient stress periods can cause a sudden increase in recharge during the transition
between these stress periods. For these circumstances it is more realistic to specify the initial water
content for the first transient stress period that follows a steady-state stress period. The option to
specify THTI in simulations that include both steady-state and one or more transient stress periods is
activated using the key word SPECIFYTHTI. This key word is input on line 1a of the UZF1 input file, and
follows the key word SPECIFYTHTR if SPECIFYTHTR is specified. Values for THTI are input following
variable THTR if it is input; otherwise, THTI follows THTS (see below).
UZF1 simulates surface leakage in the uppermost active cell if groundwater head is greater
than the top of this cell. Surface leakage is a nonlinear boundary condition that can slow model
convergence, and in some cases it is beneficial to inactive this boundary condition. Surface leakage
is inactivated by the key word NOSURFLEAK that is specified on line 1a of the UZF1 input
file. This key word is specified following the key word SPECIFYTHTI (if SPECIFYTHTI is specified).
If the key word NOSURFLEAK is specified then water will not be removed from the uppermost active cell
when groundwater head rises above the top of this cell.
In addition to these new input options, the default value for SURFDEP was changed.
In prior versions of UZF1, if the value for SURFDEP was specified as 0, it was reset
internally to 1.0. In this new version of UZF1, SURFDEP is reset to 1.0x10-6. This change
could affect simulated results if the value of SURDFEP was specified as 0 in the input file.
Modified input instructions for the UZF1 input file for specifying optional key words
0. Data: [#Text] (As in previous versions of the code)
1a. Data: [SPECIFYTHTR] [SPECIFYTHTI] [NOSURFLEAK]
SPECIFYTHTR key word for specifying optional input variable THTR.
SPECIFYTHTI key word for specifying optional input variable THTI.
NOSURFLEAK key word for inactivating calculation of surface leakage.
Note that the keywords must be entered in the order shown. For example, if keywords SPECIFYTHTR and
NOSURFLEAK are specified, then SPECIFYTHTR must precede NOSURFLEAK. Alternatively, if only SPECIFYTHTI
is specified, then the other two keywords should not be specified.
1b. Data: NUZTOP IUZFOPT IRUNFLG IETFLG IUZFCB1 IUZFCB2 NTRAIL2 NSETS2 NUZGAG SURFDEP NUZTOP
(As in previous versions of the code)
Items 2-5: As in previous versions of the code.
6a. Data: THTS (NCOL, NROW) -- U2DREL
Refer to UZF1 documentation report (Niswonger and other, 2006) for definition of THTS.
6b. Data: [THTR (NCOL, NROW)] -- U2DREL
THTR An array of positive real values used to define the residual water content for each vertical
column of cells in units of volume of water to total volume (L3L-3). THTR is the irreducible water
content and the unsaturated water content cannot drain to water contents less than THTR. This variable
is not included unless the key word SPECIFYTHTR is specified.
7. Data: [THTI (NCOL, NROW)] -- U2DREL
Refer to UZF1 documentation report (Niswonger and others, 2006) for definition of THTI. This variable is
not included for simulations with a steady-state stress period unless the key word SPECIFYTHTI is
specified.
Items 8-16: As in previous versions of the code.
Streamflow-Routing Package
Modifications were made to correct the effects of lakes inundating stream cells. Seepage in inundated
stream cells was not being set to zero in the budget routine. This change could affect mass-balance
errors for models that include lakes that grow and inundate stream cells.
Modifications were made to correct a bug that occurred when the specific yield specified in the
Block-Centered Flow (BCF7) Package was used for calculating the residual water content for the
unsaturated zone beneath streams. Changes were made such that the code searches through model layers
to find the corresponding layer that stores the specific yield for the case when the BCF7 input
variable LAYCON is 2 or 3.
Modifications were made to add a smoothing function for the calculation of wetted channel area when the
SFR2 input variable ICALC is set to 1 (constant stream width). In previous versions of the package, a
discontinuity could form if the stream channel became dry during the outer iteration of a time step,
because stream width would oscillate between the specified value and zero. To avoid such conditions, a
smoothing function was used in SFR2 to smooth the transition between the constant (specified) stream
width and a zero stream width over the interval between zero depth and 1.0x10-5 (units defined on the
basis of the DIS file input variable LENUNI). Smoothing is applied automatically if ICALC=1 and the
stream depth is between zero and 1.0x10-5 and users should refer to the calculated stream depths to
determine if smoothing was applied to a particular reach in a simulation. SFR2 smoothes the constant-
to-zero-width transition using the same smoothing function that is used by the WEL Package to decrease
specified pumping rates to zero when unconfined cells are dry (see Niswonger and others, 2011, p. 14).
Lake Package
A format statement was modified to allow proper printout of the number of dry lake cells to the main
Listing file. This change does not affect simulation results.
Source files that were modified include: NWT1_solver.f,NWT1_xmd.f,gwf2uzf1_NWT.f,gwfuzfmodule_NWT.f,
gwf2sfr7_NWT.f,gwfsfrmodule_NWT.f,gwf2lak7_NWT.f, NWT1_module.f, NWT1_gmres.f90, MF_NWT.f,
gwfsfrmodule_NWT.f, gwf2wel7_NWT.f, gwf2upw1.f, gwf2sub7.f, and gwf2hfb7_NWT.f.
o Version 1.0.2 10/03/2011:
MODFLOW-NWT was compiled again because the last release of the program required
a large amount of RAM to run models. The reason for this unnecessary memory usage
was not determined but it is assumed that the issue was related to the compiler.
The new compiled version requires much less memory. For example, a model that
required 2 Gb of memory to run now requires 120 Mb. This new memory usage
is consistent with what is required by MODFLOW-2005.
Changes were made to the MODFLOW-NWT source files such that residual-control
(backtracking) iterations are no longer counted as outer iterations. This change
affects the NWT solver iteration information that is printed to the main List file.
Another change was made to stop model execution when the convergence criteria are not met.
In previous versions of MODFLOW-NWT, the model continued to solve after the model
failed to converge. A keyword option was added to the NWT Package input file to
allow the user to control whether the model will stop after convergence failure.
If the keyword "CONTINUE" is added following the input variable OPTIONS then the model
will not stop after convergence failure. If this keyword is not specified then the
model will stop after convergence failure. For example, the key word "CONTINUE" can
be added to the first line of the NWT input file as:
1.0E-4 1. 500 1.0e-5 2 1 1 SPECIFIED CONTINUE 0.9 0.00001 0.000 0.10 0 20 2.0 0.6
For this input option, if the model fails to converge during a time step then it
will continue to the next time step. However, if the "CONTINUE" is removed
from this line, then the model will stop after convergence failure.
Another change was made to fix a bug that caused the model to print a blank line
to the main List file rather than correctly printing the string "SPECIFIC YIELD
FOR LAYER..." This change does not affect model results.
Another change was made to modify how groundwater heads are reset to the layer-
bottom altitude when the calculated heads are below the bottom of the deepest layer.
In the previous version of the code there was a condition when heads could be
reset to an incorrect value, and this caused small oscillations in some problems.
This change may have a small affect to improve model convergence if the NWT input
variable IBOTAV is equal to 1.
Another change was made to fix oscillatory behavior caused by a feature in the MNW2
and MNW1 packages. The original versions of these packages switched between
a specified flux and a head-dependent boundary conditions during outer iterations.
The MNW1 and MNW2 packages were modified such that the boundary condition is
fixed as a head-dependent boundary condition.
A small change was made in the XMD source file to allow for double precision
compilations. This change was to change the statement from real*4 to real.
Small changes were made to the UZF1 and SFR2 source files to improve standard
output options.
Changes were made to the MT3DMS linker files (lmt7_NWT.f, and lmt7_NWT.inc) to
include water balance information for the MNW2 and MNW1 packages.
Source files that were modified include: MF_NWT.f, NWT1_solver.f, NWT1_xmd.f,
gwf2MNW27_NWT.f, gwf2MNW17_NWT.f, gwf2sfr7_NWT.f, gwf2upw1.f, gwfsfrmodule_NWT.f,
gwf2uzf1_NWT.f, gwfuzfmodule_NWT.f, lmt7_NWT.f, and lmt7_NWT.inc.
o Version 1.0.1 05/27/2011:
Changes were made to the MODFLOW-NWT source files to correct an error in how the
Horizontal-Flow (HFB) Barrier Package was implemented in MODFLOW-NWT. Additionally,
changes were made to deallocate arrays in the XMD and GMRES solvers at the termination
of a simulation.
Source files that were modified include: MF_NWT.f, NWT1_solver.f, NWT1_xmd.f,
gwf2hfb7_NWT.f, NWT1_gmres.f90, and gwf2bas7.f
o Version 1.0 05/11/2011:
This version is the initial release. However, a number of changes were required
for four additional MODFLOW-2005 Packages that were not explained in the
MODFLOW-NWT documentation report (Niswonger and others, 2011). The modified
packages include the Horizontal-Flow Barrier, Lake, and Multi-Node Well Packages
versions 1 and 2.
Changes to the Horizontal-Flow (HFB) Barrier Package were made to the subroutine
GWF2HFB7FM. If the Newton method is used in MODFLOW-NWT, then horizontal
conductances do not include the aquifer thickness for unconfined conditions.
Thus, equations were changed such that the conductances modified in subroutine
GWF2HFB7FM are not multiplied by the aquifer thickness. This change required that
a new argument be added to the call statement for subroutine GWF2HFB7FM to include
the file unit number for the UPW Package.
Changes to the Lake (LAK) Package were made to the subroutine GWF2LAK7RP and a new
subroutine was added to the LAK Package called SGWF2LAK7UPW1RPS for calculating
lakebed conductance values. This change required that a new argument be added to
the call statement for subroutine GWF2LAK7RP to include the file unit number for
the UPW Package.
Changes to Versions 1 and 2 of the multi-Node Well (MNW1 and MNW2) Packages were
made to the subroutines GWF2MNW17RP and GWF2MNW27RP. A new subroutine was added to
the MNW1 and MNW2 Packages called CEL2WELUPW for calculating well conductance
values. A new argument was added to the call statement for subroutines GWF2MNW17RP
and GWF2MNW27RP to include the file unit number for the UPW Package.
References
Anderman, E. R., & Hill, M. C. (2000). MODFLOW-2000: The US Geological Survey Modular Ground-water
Model--documentation of the Hydrogeologic-Unit Flow (HUF) Package. US Department of the Interior,
US Geological Survey.
Bakker, Mark, Schaars, Frans, Hughes, J.D., Langevin, C.D., and Dausman, A.M., 2013,
Documentation of the seawater intrusion (SWI2) package for MODFLOW: U.S. Geological Survey
Techniques and Methods, book 6, chap. A46, 47 p.
Hughes, J.D., Langevin, C.D., Chartier, K.L., and White, J.T., 2012, Documentation of the Surface-Water
Routing (SWR1) Process for modeling surface-water flow with the U.S. Geological Survey Modular Ground-Water
Model (MODFLOW-2005): U.S. Geological Survey Techniques and Methods, book 6, chap. A40 (Version 1.0), 113 p.
Konikow, L.F., Hornberger, G.Z., Halford, K.J., and Hanson, R.T., 2009, Revised multi-node well
(MNW2) package for MODFLOW ground-water flow model: U.S. Geological Survey Techniques and Methods
6ľA30, 67 p.
Niswonger, R.G., Panday, Sorab, and Ibaraki, Motomu, 2011, MODFLOW-NWT, A Newton formulation for
MODFLOW-2005: U.S. Geological Survey Techniques and Methods 6-A37, 44 p.
Niswonger, R.G., Prudic, D.E., and Regan, R.S., 2006, Documentation of the Unsaturated-Zone Flow (UZF1)
Package for modeling unsaturated flow between the land surface and the water table with MODFLOW-2005:
U.S. Geological Survey Techniques and Methods 6-A19, 62 p.